Legal basis and necessity
Processing is allowed on the ground of legitimate interests, except where the interests or fundamental rights of the data subject override them [1]. You collect no more than necessary for the purpose [2]. An online profile can be relevant for a position in which that profile plays a role; a general search into private life rarely is.
Sensitive data
As a rule you may not process data revealing, for example, race, political opinions, religious belief or sexual orientation [3]. Make sure a tool that picks up such information does not take it into account.
Informing the applicant
If you do not obtain data from the applicant themselves, you state, among other things, the purpose and the categories of data [4] and the source the data comes from, even if it is public [5]. You do so within a month, and at the latest at the first contact if you use the data to communicate with them [6].
From 2027: high-risk
AI for analysing and filtering applications and evaluating candidates is on the high-risk list [7], with duties from 2 December 2027 [8].